linux-kernel - Re: [PATCH] i2c: imx: increase retries on arbitration loss

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Message-ID: <20221216094518.bevkg5buzu7iybfh@pengutronix.de>
Date:   Fri, 16 Dec 2022 10:45:18 +0100
From:   Marco Felsch <m.felsch@...gutronix.de>
To:     Primoz Fiser <primoz.fiser@...ik.com>
Cc:     Oleksij Rempel <linux@...pel-privat.de>,
        Pengutronix Kernel Team <kernel@...gutronix.de>,
        Shawn Guo <shawnguo@...nel.org>,
        Sascha Hauer <s.hauer@...gutronix.de>,
        Fabio Estevam <festevam@...il.com>,
        NXP Linux Team <linux-imx@....com>,
        linux-i2c@...r.kernel.org, linux-arm-kernel@...ts.infradead.org,
        linux-kernel@...r.kernel.org, upstream@...ts.phytec.de
Subject: Re: [PATCH] i2c: imx: increase retries on arbitration loss

Hi Primoz,

On 22-12-16, Primoz Fiser wrote:
> By default, retries value is set to 0 (no retries). Set retries to more
> sensible value of 3 to allow i2c core to re-attempt transfer in case of
> i2c arbitration loss (i2c-imx returns -EAGAIN errno is such case).

apart the fact that the number of retries vary a lot and so the client
driver behaviour can vary a lot which is not good IMHO, why do you think
that 3 is a sufficient number?

If an arbitration loss happen, why do you think that retrying it 3 times
changes that?

Regards,
  Marco


> 
> Signed-off-by: Primoz Fiser <primoz.fiser@...ik.com>
> ---
>  drivers/i2c/busses/i2c-imx.c | 1 +
>  1 file changed, 1 insertion(+)
> 
> diff --git a/drivers/i2c/busses/i2c-imx.c b/drivers/i2c/busses/i2c-imx.c
> index cf5bacf3a488..6a5694cfe1cc 100644
> --- a/drivers/i2c/busses/i2c-imx.c
> +++ b/drivers/i2c/busses/i2c-imx.c
> @@ -1478,6 +1478,7 @@ static int i2c_imx_probe(struct platform_device *pdev)
>  	i2c_imx->adapter.dev.parent	= &pdev->dev;
>  	i2c_imx->adapter.nr		= pdev->id;
>  	i2c_imx->adapter.dev.of_node	= pdev->dev.of_node;
> +	i2c_imx->adapter.retries	= 3;
>  	i2c_imx->base			= base;
>  	ACPI_COMPANION_SET(&i2c_imx->adapter.dev, ACPI_COMPANION(&pdev->dev));
>  
> -- 
> 2.25.1
> 
> 
>